Anytime you kill a drug dealer, you will net $2000. Drug dealers normally wear black jackets and stand still waiting for people to talk to them. Kill as many as you can find to build up your cash stash quickly.

To earn some easy weapon skill, go and practice with an AK-47 before starting this mission until you reach Gangster level. Then while in the mission, blast on as many cop cars and bikes as possible. You'll deal out so much damage that there is a very high chance of you reaching Hitman weapon skill level.

To earn easy weapon skill, go and get any 2 cars and place them in your Grove St home garage. Then with the weapon of your choice shoot the cars until they are nearly on fire. Then walk away from the garage so it can close. Walk up to the garage again and you will notice that the cars are repaired. Repeat this process as it is one of the fastest ways to earn weapon skill in the game. To check your progress with weapon skill, switch to the weapon that you want to check and then go to STATS in the menu and then go down to WEAPONS. The number there is how many skill points you have. You need 1000 skill points to reach hitman level.